Conventionally disclosed is a thin film transistor that includes a gate insulating layer made of a ferroelectric material (e.g. BLT (Bi4-XLaXTi3O12) or PZT (Pb(ZrX, Ti1-X)O3)) in order to enable rapid switching at a low drive voltage. Meanwhile, also disclosed in order to increase carrier density is a thin film transistor that includes a channel made of an oxide conductive material (e.g. indium tin oxide (ITO), zinc oxide (ZnO), or LSCO (LaXSr1-XCuO4)) (Patent Document 1).
In a method for manufacturing the thin film transistor mentioned above, a gate electrode of laminated films made of Ti and Pt is formed in accordance with an electron-beam evaporation technique. The gate insulating layer made of BLT or PZT is formed on the gate electrode in accordance with a sol-gel technique. The channel made of ITO is further formed on the gate insulating layer in accordance with a RF-sputtering technique. Subsequently formed on the channel are Ti and Pt serving as a source electrode and a drain electrode in accordance with an electron-beam evaporation technique. An element region is then isolated from a different element region in accordance with a RIE technique and a wet etching technique (using a mixed solution of HF and HCl) (Patent Document 1). The inventors of this application have studied selection and combination of oxide that appropriately exhibits functions as a thin film transistor (Patent Document 2).